In semiconductor manufacturing equipment, chemical reactions of various kinds of gases are used to form layers on a wafer board. A process chamber where chemical reactions take place, should be in conditions in which contaminant materials and unnecessary elements are not present.
Recently, semiconductor devices are becoming integrated, and the manufacturing yield of semiconductor devices may be lowered due to a small difference in processing conditions of the process chamber. For example, after layers are deposited or etched by reactions between gases, gases remaining in forms of unreacted gases or reaction byproducts may affect subsequent processes, causing a reduction in the yield or other failures.
Therefore, in order to control in advance various failures which may occur in the semiconductor manufacturing process or to identify a state of an ongoing process, it is desirable to monitor changes in chemical components and concentrations of gases in the process chamber on a real time basis.
A residual gas analyzer (RGA) analyzes the components and concentration of a sample gas by sampling some of the gas flowing in a vent line after a reaction takes place in a process chamber, decomposing the sample gas into a radical gas using high voltage energy and measuring a mass of the decomposed gas. That is to say, the components and concentration of the sample gas are analyzed by measuring a current value of positive ions of ionized sample gas. In addition to the residual gas analyzer (RGA), an on-line time-of-flight (ToF) analyzer, or a Fourier Transform Infrared (FT-IR) analyzer may also be used to analyze the components and concentration of the sample gas.